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TELEVISION Filed May 20, 1926 3 Sheets-meet E 'atenteil Doc. 3, 1929UNITED.; STATES -I=-ATENT OFFICE `:HERBERTl E. IVRB, l' IONTCLAIR, NRWJERSEY, ABBIGNOR T0 BELL TELEPHONE LABORATORIES, INCORPORATED, 0F NEWYORK, N. Y., .A OQRPORATION 0l'- NRW 'YORK 'rmvrsroir Application liedlay 50, 1926. Serial Ie. 110,878.

This invention relates to the electricaly transmission of scenes orpictures and particularly to the reproduction of such scenes or picturesin their natural colors.

a It is the principal object of the presentinvention to improve thescanning of a picture er view being transmitted. e

It is well known in the art that pictures may be transmitted by meansof'an electriwhich is generated corresponding to the light intensity ofsuccessive small areas of the pieture, is used to modulate a carriercurrent. 'Ihis current is demodulated at a receiving station to controlthe intensity of illumination of a lamp or lamps. A variety of scanningmeans have been proposed, one commonly used consisting of a rotatingdisc having a plurality of apertures therein arranged in color ithasbeenlustomary either to make a record of the colds-valuesv in thepicture and use these recprds for generating the photoelectric currentor to use a plurality of carrier currents for carrying the photoelectricvariations where that' current 1s generated directly. In either case thedemodulated carrier current has been used to make black and Whiterecords -which are subsequently used to control the production of thecolored picture. l

According to the present inventlon the scene to be transmitted isscanned repeatedly and successively for each of a plural1ty oi primarycolors. At the receiving station images are repeatedly produced in eachof the primary colors in turn and pro]ected on a screen at such a speedthat the eye combines the colors. According to a modiication of theinvention the object is scanned in strips, successive strips beingscanned for different colors and the order of the colors being changedfor successive complete scannings.

The receiving apparatus is arranged to reproduce the icture in strips ofcorrespondin color an to shift the color 1n the same or er as thetransmitting apparatus.

In brief, there is employed, in a system hereinafter described as aspecific and illustrattive embodiment of the invention, a plucal systemwherein a photoelectric current,.

in a spiral. In the reproduction of pictures rality of photoelectriccells each responsive to a different re 'on of the spectrum with anarrangement o?! rotating mirrors, eachv of which directs the light toall of the vcells in succession. Thev picture or view is scanned bymeans of a rotating disc having spirally arranged apertures therein andthe light which passes through the apertures is directed to the rotatingmirror. At the receivmg end a plurality of lamps each emitting light ofa different region of the spectrum, are lighted by current received overthe line. A mirror arrangement and scanning disc similar to those at thesending station serve to reproduce the picture on a screen at therecelvmg station.

I n the modified form of the invention a series of lenses and mirrorsdirect the light from the scanning disc to photoelectric cells whichrespond to light from diierent regions of t e spectrum. A commutatingdevice connects these cells successively to a carrier wave modulator.The scannin disc and the commutator are driven simu taneously so thateach cell is associated with the modulator for only a ortion of arevolution of the scanning disc. owever, the scanning disc is geared tothe drivin mechanism of the commutator so as to ma e slightly more orslightly less than one revolution per revolution of the commutator, thusshifting the order in which the photoelectric cells are connested to themodulator for successive scannings of the object. At the receivingstation the commutatorand scanning disc are similarly arranged and theimage is produced in strips.

In the drawings two modifications of such a systemre shown. Figs. 1 and2 show an organization whereby the icture may be completely scanned foreac color in succession. Fig. 3 shows an organization whereby thepicture may be scanned in strips.

Referring to the embodiment shown in Figs. 1 and 2, the picture to betransmitted is represented by film 100 which is illuminated in anysuitable manner, for exam le, by lamp 101 4and condensing lens 102. ilm100 indicates a single picture which may be one from a strip 24revolutions to one amplifier 222, and

such as used in projecting .a motion picture. Lens 104 produces an lmageof the film upon the scanning disc 105 and lens 106 focuses a beam oflight on the fphotoelectric cells 107, 108 and 109 after re ection bythe rotating mirror 110.

If the object to be transmitted is not a picture but a natural scene,the lens 104 may be used to form' an image of the scene directly on thedisc. The scanning disc and the rotating mirror are drivensimultaneously under th control of tuning fork 111. Tuning fork 111 maybe driven by means of the usual self- `interrupting circuit orby. anyother desirable ,means The tunin fork in vibratin closes obvious circuitf or operating the La Cour motor 112 whici turns the shaft 113. The disc114, rigidly attached to the shaft 113, is geared to scanning disc 105,discs 114 and 105 beingof the same size so that a single -rotation ofthe shaft 113 produces a single rotation of the scanning disc. Shaft 113is also suitably coupled to the Geneva movement 115. From an inspectionof the drawing it will be apparent that for each revolution of disc 116,disc 117 will make a quarter turn. The driving disc 118 and driven disc119, which is rigidly attached to the multifaced mirror 110, are gearedin the ratio of 1 to 6. Therefore scanning disc 105 will make completerevolution of mirror 110.

The tuning fork 111 also serves to control the synchronous movement ofthe driving apparatus at the receiving station. This driving apparatuscomprises a tuning fork 211, a La Cour motor 212 and a Geneva movement215 and serves to drive a scanning disc 205' anda multi-faced mirror 210at speeds bearing the ratio of 1 to 24. A source of current 120, amodulator 121 controlled by fork 11, an amplifier 122, and a filter 123transmit a synchronizing current to the line At the receiving station afilter 223, an a demodulator 221 cause the energization of a magnet 224in synchronism with magnet 124 to drive the tuning fork 211. Suitableapparatus for producing and receiving the synchronizing current isdescribed in the patent of Maurice B. Long, No. 1,706,032, issued March19, 1929.

Considering the optical arrangement in detail for a moment, with themirror 110 in the osition shown, light from the disc 105 will Eedirected upon photoelectric cell 107. As each aperture of the discpasses across the image of the film, a spot of light of varyingintensity will be focused upon cell 107. The b not completely endapertures in disc 105 do circle the disc but are arranged to leave asection of the Vdisc solid. The discs of the Geneva movement 116 and 117are arranged so that pin 125 engages slot 126 and the mirror is movedforward While no apertures are passing the image of the film. Theadvance of the lwhich responds to the green region of the spectrum andthe third quarter turn brings face 128 into the position which face 127occu ies `in the drawing.

' he im edance of the photoelectric cells, particular y when notilluminated, is sufiiciently high so that Ythe connection of the darkcells in parallel with the cell receiving the incident light does notmaterially reduce the photoelectric current. The amplifier 180 amplifiesthe photoelectric current before its application to modulator 142. Asthe beam of light is successfully directed upon cells 107, 108 and 109,the photoelectric current will represent the variations of thecorresponding color in the image.

Oscillator 141, modulator 142, amplifier 143 and filter 144 serve totransmit a carrier wave modulated by the current in the photoelectriccells to the line L While filter 244, amplifier 2,43 and demodulator 242receive the modulated waves and direct the signal current to lamps 207,208 and 209. Reference is made to the above identified Long applicationfor the disclosure of these elements.

At the receiving end lamp 207 emits light from the red end-of thespectrum, lamp 208 from the een region of the spectrum and lamp 209 romthe blue end of the spectrum. These lamps are lighted simultaneously butas mirror 210 rotates, light from only one lamp at a time is directed tothe disc 205 and an image of the aperture is projected on the screen290.

To recapitulate, as the mirror 110 rotates under the control of fork111, disc 105 is rotated and as each successive aperture in the spiralpasses across the image formed on the disc, the spot of light focused onone of the photoelectric cells, say 107, varies inI intensity inaccordance with the brightness of the image being scanned. This spot oflight will contain all of the colors but, since cell 107 is responsiveto red light only, it will produce a variation of current in themodulating circuit in accordance with the variation of red light in theimage. At the next revolution of disc 105 the spot of light will edirected to cell 109 and that c ell will prouce a current whichrepresents the strength of blue light in the image. Similarly, on thethird revolution the current in the modulating circuit will representthe strength of green light in the image. Successive revolutions willcause a modulating current representing the colors in rotation.

lo vary with the strength of Q green ima e.

igvsspov At the reeeivin end the drivingI apparatus being in sync ronismwith that at the sending Station, the light'from lamp 207 will bedirected on scanning disc 205" at the .same time that light is focusedon cell 107. *The current leaving the demodulator 242 varies inaccordance with the variations in v the current reaching modulator 142and the illumination of lamps 207 208 and 209 will A the red color inthe light focused on cel1107. vSince only the light of lamp 207 will bedirected on the disc 205 this disc in rotating will cause va spot oflight to travel over the screen 290.v This u spot of light will be redin color and will vary in intensity with the red in the original image.During the second revolution of disc 205 a blue image will be thrown onthe screen 290 and on the third revolution a These images will followone another with such rapidity that the eye of the observer cannotdistinguish between them and the resultant effect on the retina will bea picture in the colors of the orig- @5 lllal.

Referring now to Fig. 3 a system is disclosed in which the picture orscene is scanned in strips, eachfstrip belng scanned for a differentcolor and the order of the w colors being altered for each completescanning. For this purpose, the film 311 represents the picture or sceneto be scanned., an image of which is formed on the scanning disc 301 bythe lens 302. A. series of semi-transparent mirrors and lenses serves todirect a portion of the light from the scanning disc 301 to each of thephotoelectric cells303, 304 and 305. These light cells are maderesponsive to red, green and blue lights respectively b using mirrorswhich reflect the desired lig t, by the interposition of color'liltersor by making the cells themselves responsive only to the color desired.

The scannin disc 301 is driven through the agency o a tuning forkcontrolled La Cour motor which also drivesa commutating arrangement 306.The driving disc 307 bears an unequal ratio to the scanning disc 301,for example, 16 to 15. The fork also sends out impulses which serve tosynchronize the driving apparatus at the receiving station 350, whichapparatus is a duplicate of that at the sending station 300. Theapparatus for transmitting and receiving these synchronizing impulsesmay be of any desirable ty e, such as that shown in the above identi edLong application.

Referring to the commutating arrangement, brush 308 serves to connectring 309 with the ring ofnsegments 310. These segments are connected tothe photoelectric cells 303., 304 and 305. The sequence of colors forwhich the picture will be scanned may be readily determined from aninspection of 05 the drawing. With the suggested ratio of 15v to 16between the driving and scanning discs it will be apparent that therelation between the stri of the picture scanned and the color for w ichthat picture is scanned will be changed at each revolution.

The current produced in each of the cells due to the intensity of thecorresponding light in the beam from the scanning disc 301 istransmitted over the line L and received in the usual manner. A lamp isprovided for each color and a plurality of semitransparent mirrors andlenses to produce a spot of colored light on the screen. As in the caseof the sending station, the color may be controlled either by the colorof the lamps or by the colorf the mirrors. The driving arrangement atthe receiving end is similar to that at the sending station and acommutating arrangement 356 serves to conneet the lamps with the line inthe same order as the photoelectric cells are by the commutatingarrangement 306.

The apparatus shown is of course merely suggestive. For example, asingle photoelectric cell may be used and a Geneva move ment may beemployed to introduce colored filters between the scannin disc 'and thecell at the sending station and etween the lamp and the scanning disc atthe receiving station. According to a modication of the arrangementshown in Fig. 3 opaque screens may be used to obscure all but onephotoelectric cell and lamp at a time.` It is therefore apparent that itmay be possible, without departing from the spirit of thinven tion, toemp oy equivalents for many parts of the system.

What is claimed is:

1. In a system for the transmission. oi

views, means for repeatedly scanning the view including a plurality ofselective light responsive elements and means for illuminating saidelementsin' succession by light of different colors respectively fromsaid view, sources of light of different colors, means for renderingsaid light responsive elements successively effective for controllingthe light from said sources, and means for synthesizing the light fromsaid sources to produce an image.

2. In a system for the transmission ofy views, a plurality of selectivelight translating elements, means to repeatedly and successively scanthe view for each of a plurality of colors one at a time, and means forreproducing said view in its natural colors by the repeated andsuccessive production of an image for each of said plurality of colors.

3. In a system -or the transmission of Views, means to repeatedly andsuccessively scan the view for each of a plurality of colors one at atime, means for translating the view into an electrical currentproportional successively to the amount of each primary color in saidview, means for producing light of each primary color, means foractuating said light producing means under the control of saidelectrical current, and means for synthesizing the light produced bysaid light pro- 5 ducin means to reproduce said view.

4. liil a system for the transmission of views, means for repeatedly andsuccessively scanning the view for each of a plurality of colors one ata time, a plurality ofphotoelec- 1;, tric cells, each responsive to aparticular color, means for rendering said photoelectric cells'effective in a predetermined order, a plurality of lamps, each lampemitting a particular color, means for varying the illumination of eachlamp in accordance with the current produced by the photoelect'ric cellin response to the corresponding color, and means for synthesizing thecolored light from said lamps to reproduce the view in its naturalcolors.

.5. In a system for the transmission of views, means for scanningelementary areas of said View to produce an electric currentcorresponding to the Variation of the light value of a primary color insaid elementary areas, means for varying the color for the scanning ofsuccessive elementary areas,

means for varying the color for successive scannings of the sameelementary area, means for transmitting and receiving said current,

' a0 and means for reproducing elementary areas of corresponding colorto produce an image in its natural colors.

6. The method of transmitting and reproducing views in color which`consists in scan- 85 ning successive elementary areas of said image fordiferent colors, changing the order of said colors for successivescannings of said image, transmitting an electric current varyingaccording to the light value of the colors,

40 and at the receiving end reproducing elementary areas of the image inthe corresponding nolors.

7. The combination in a system for transmitting views of a plurality ofphotoelectric cells selectively responsive to light of different colors,a disc with spirally arranged apertures thereinv for scanning the view,a system of mirrors cooperating with said disc for directing light fromsaid view successively and l0 repeatedly t0 said cells, means fortransmitting an e ectric current varied in accordance with thephotoelectric response of said cells, a plurality of lamps each emittinglight of a diierent color, means responsive to the vtrans- IB mittedcurrent for controlling the intensity of the light from said lamps, andmeans including a disc with spirally arranged apertures and a mirrorsystem for combining the light from said lamps to form an image of thesaid W view in its natural colors.

In witness whereof, I hereunto subscribe my name this 19th day7 of May.A. D. 1926. HERBERT E. IVES.

